Feedback control for lidar using principles of direct atomic vapor absorption

Abstract

A direct detection LIght Detection and Ranging (“LIDAR”) system for instantaneous measurement of target velocity and distance uses principles of dichroic atomic vapor absorption in a closed feedback loop. In one or more embodiments, the system includes a laser light source to transmit laser light toward a target; a Dichroic Atomic Vapor Laser Locking (“DAVLL”) system including a gas cell in a magnetic field, wherein the DAVLL system is coupled to receive the laser light after being reflected by the target and output an error signal that can be used to calculated the relative velocity between the emitter and the target; and a feedback control configured to determine respective gas absorption rates of the LCP and RCP light beams in the gas cell, determine a difference of the respective gas absorption rates, and control the laser light source to adjust the frequency of the transmitted laser light in accordance with the determined ratio.

What is claimed is: 
     
         1 . A LIDAR system, comprising:
 a laser light source to transmit laser light toward a target;   a DAVLL system including a gas cell in a magnetic field, wherein the DAVLL system is coupled to receive the laser light after being reflected by the target and output an error signal related to the frequency offset between the transmitting laser and the gas absorption line center and the frequency offset between the received light from a target and the gas absorption line center; and   a feedback control configured to determine respective gas absorption rates of the LCP and RCP light beams in the gas cell, determine a difference of the respective gas absorption rates, and control the laser light source to adjust the frequency of the transmitted laser light in accordance with the determined ratio.   
     
     
         2 . The LIDAR system of  claim 1 , further comprising a processor configured to compute a speed of the target in accordance with the determined ratio. 
     
     
         3 . The LIDAR system of  claim 2 , wherein the processor is further configured to compute a distance to the target in accordance with the determined ratio. 
     
     
         4 . The LIDAR system of  claim 1 , wherein the feedback control is configured to control the laser light source to adjust the frequency of the transmitted laser light to the frequency at the gas absorption line center.